The subject matter disclosed herein generally relates to airflow in components of gas turbine engines and, more particularly, to dual-fed airfoil tips in components of gas turbine engines.
Airfoils, and particularly airfoils of gas turbine engines, may include internal flow passages to enable cooling of the airfoils. At various points within the airfoil cooling configurations, air may be bled from and/or between the internal flow passages. In gas turbine engines, one way to improve efficiency is by increasing the pressure and temperature of the compressed and combusted air, from which the turbine extracts work. Thus more highly-evolved turbines see ever-increasing gaspath and cooling air temperatures, which presents a challenge as the gaspath temperatures often exceed incipient melting temperatures of the constituent alloys of the airfoils. Complex internal cooling schemes may be configured to supply convective cooling and source film cooling. The airfoils may be produced by methods commonly used in the investment casting process of superalloys with alumina or silica ceramic cores, as well as, produced using additive manufacturing processes to directly fabricate the core by using Direct Metal Laser Sintering (SMLS) and/or Electron Beam Machining (EBM) processes.
The supply of the cooling air through cavities of the airfoils may be carefully designed so as to provide an efficient cooling configuration. As the amount of cooling air required to convectively and/or film cool greater heat loads increases, the areas through which the cooling air must pass to serve its function do not necessarily proportionally increase. This presents an issue as there are deleterious effects associated with increasing the Mach number through the internal cavities of the airfoil. A common “pinch point” where a cavity Mach number may increase above an acceptable level is in the neck of an airfoil near the radial level of the platform, affecting typically leading-edge and trailing-edge feeds.
At the same time, it is often desirable to provide a tip flag cavity underneath or within the proximity of the tip of an airfoil (e.g., a high pressure turbine blade), which is traditionally fed from a leading-edge feed cavity. The cooling air supply requirement for this cavity may increase the demand on the leading-edge feed, at times, to supply cooling air above an optimal level of flow.